Longitudinally flexible expandable stent

ABSTRACT

Segmented articulatable stent of open structure comprised of end-connected struts of first and second lengths making up first and second segments with angular interconnects between adjacent first and second segments.

This application is a Continuation-in-Part of application Ser. No.08/511,076, filed Aug. 3, 1995, the disclosure of which is herebyincorporated by reference.

FIELD OF THE INVENTION

This invention relates to an endoprosthesis device for implantationwithin a body vessel, typically a blood vessel. More specifically, itrelates to a tubular expandable stent of improved longitudinalflexibility.

BACKGROUND OF THE INVENTION

Stents are placed or implanted within a blood vessel for treatingstenoses, strictures or aneurysms therein. They are implanted toreinforce collapsing, partially occluded, weakened, or dilated sectionsof a blood vessel. They have also been implanted in the urinary tractand in bile ducts.

Typically, a stent will have an unexpanded (closed) diameter forplacement and an expanded (opened) diameter after placement in thevessel or the duct. Some stents are self-expanding and some are expandedmechanically with radial outward force from within the stent, as byinflation of a balloon.

An example of the latter type is shown in U.S. Pat. No. 4,733,665 toPalmaz, which issued Mar. 29, 1988, and discloses a number of stentconfigurations for implantation with the aid of a catheter. The catheterincludes an arrangement wherein a balloon inside the stent is inflatedto expand the stent by plastically deforming it, after positioning itwithin a blood vessel.

A type of self-expanding stent is described in U.S. Pat. No. 4,503,569to Dotter which issued Mar. 12, 1985, and discloses a shape memory stentwhich expands to an implanted configuration with a change intemperature. Other types of self-expanding stents not made of shapememory material are also known.

This invention is directed to stents of all these types when configuredso as to be longitudinally flexible as described in detail hereinbelow.Flexibility is a desirable feature in a stent so as to conform to bendsin a vessel. Such stents are known in the prior art. Examples are shownin U.S. Pat. No. 4,856,516 to Hillstead; U.S. Pat. No. 5,104,404 toWolff; U.S. Pat. No. 4,994,071 to MacGregor; U.S. Pat. No. 5,102,417 toPalmaz; U.S. Pat. No. 5,195,984 to Schatz; U.S. Pat. No. 5,135,536 toHillstead; U.S. Pat. No. 5,354,309 to Shepp-Pesch et al.; EPO PatentApplication 0 540 290 A2 to Lau; EPO Patent Application No. 0 364 787 BIto Schatz, and PCT Application WO 94/17754 (also identified as GermanPatent Application 43 03 181).

Generally speaking, these kinds of stents are articulated and areusually formed of a plurality of aligned, expandable, relativelyinflexible, circular segments which are interconnected by flexibleelements to form a generally tubular body which is capable of a degreeof articulation or bending. Unfortunately, a problem with such stents isthat binding, overlapping or interference can occur between adjacentsegments on the inside of a bend due to the segments moving toward eachother and into contact or on the outside of a bend the segments can moveaway from each other, leaving large gaps. This can lead to impropervessel support, vessel trauma, flow disturbance, kinking, balloon burstduring expansion, and difficult recross for devices to be installedthrough already implanted devices and to unsupported regions of vessel.

A diamond configuration with diagonal connections between each and everydiamond of each segment is also known but such closed configurationslack flexibility.

It is an object of this invention to provide a longitudinally flexiblestent of open configuration that avoids these problems and exhibitsimproved flexibility (radially and longitudinally) in the stent bodysegments thereof rather than in flexible joints between the segments.

It is a further object of the present invention to provide a stent thatis flexible yet also allows for side branch access.

SUMMARY OF THE INVENTION

It is a goal of the present invention to provide a flexible stent formedof interconnected bands which provides for side branch access and whichfurther avoids the problem of pinching or overlap between adjacentbands. Pinching or overlap is avoided where peaks and troughs ofadjacent bands are circumferentially displaced relative to each other.The stents of the present invention accomplish this goal by havingdifferent bands characterized by different wavelengths over the lengthof the stent and/or disposing the interconnecting members in such a waythat after expansion of the stent, the phase relationship betweenadjacent bands is altered with the peaks and troughs displacedcircumferentially relative to each other.

The inventive expandable stents are formed of a plurality ofinterconnected band-like elements characterized by alternating peaks andtroughs. The ends of the interconnecting members which join adjacentbands are circumferentially offset and optionally, longitudinallyoffset. Peaks and troughs in adjacent bands are circumferentially offsetas well so that the stent, in an expanded state, will have minimaloverlap of peaks and troughs.

To this end, the invention provides a tubular, flexible, expandablestent, comprising a plurality of undulating band-like elements of aselected wavelength or wavelengths. The band-like elements have peaksand troughs and are aligned on a common longitudinal axis to define agenerally tubular stent body. The peaks and troughs take a generallylongitudinal direction along the stent body. Adjacent band-like elementsmay be in phase or out of phase with each other. The inventive stentsfurther comprise a plurality of interconnecting elements having firstends and second ends. The first and second ends extend from adjacentband-like elements and are displaced from one another in a longitudinaldirection and in a radial direction along the stent. Desirably, uponexpansion of the stent, at least some of the peaks and troughs of agiven band-like element are displaced relative to each other about theperiphery of the stent to accommodate longitudinal flexing of the stentwithin the band-like elements and without interference between adjacentband-like elements.

In one embodiment, two different types of band-like elements are presentin the stent, first band-like elements with a first selected wavelengthand second band-like elements with a second selected wavelengthexceeding the first selected wavelength. The first and second band-likeelements preferably alternate over the length of the stent. Although theterminology of ‘first band-like element’ and ‘second band-like element’is used, it is not intended to convey the relative order of appearanceof the elements in the inventive stents.

In another embodiment, two different types of band-like elements arepresent, first and second band-like elements, each of which has peaksand troughs. The first band-like elements have more peaks (or troughs)than the second band-like elements. Similarly, the invention is alsodirected to embodiments having first and second band-like elements withpeaks and troughs where the peaks (or troughs) of the first band-likeelements are spaced closer together than the peaks (or troughs) of thesecond band-like elements.

In another embodiment in which band-like elements of only one wavelengthare present, adjacent bands are about 180° out of phase with oneanother. Interconnecting elements extend at an oblique angle relative tothe longitudinal axis from a peak to a trough on an adjacent band.

In another embodiment in which band-like elements of only one wavelengthare present, peaks from which interconnecting elements emanate areelongated relative to the peaks which are not connected to troughs andsimilarly, the troughs from which interconnectors emanate are elongatedrelative to troughs which are not connected to peaks. Further, eachinterconnecting element extends from the side of a peak to the side of atrough on an adjacent band.

In yet another embodiment in which band-like elements of only onewavelength are present, adjacent bands are about 90° out of phase withone another. Each interconnecting element extends between a peak and atrough and the ends of the interconnecting member are circumferentiallyoffset from one another and, optionally, longitudinally offset.

The invention further provides a tubular, flexible, expandable stenthaving a longitudinal axis, comprising one or more cylindrical shapedfirst segments having first struts, the first segment being defined by amember formed in an undulating pattern of interconnected paired firststruts and in which adjacent pairs of first struts in a given firstsegment are interconnected at opposite ends and one or more cylindricalshaped second segments defined by a member formed in an undulatingpattern of interconnected paired second struts and in which adjacentpairs of second struts in a given second segment are interconnected atopposite ends. The first struts are shorter than the second struts. Thefirst segments are formed of a number of first struts and the secondsegments are formed of a number of second struts with the number offirst struts in a first segment exceeding the number of second struts ina second segment. The first and second segments, present and desirablyalternating along the stent body, are aligned on a common longitudinalaxis to define a generally tubular stent body. Adjacent first and secondsegments are connected by a plurality of interconnecting elements, eachinterconnecting element extending from an end of paired first struts ona first segment to an end of paired second struts on an adjacent secondsegment. The ends of interconnecting elements are circumferentiallyoffset relative to each other, and optionally, longitudinally offset.Desirably, upon expansion of the stent, the paired struts of theadjacent segments are displaced relative to each other about theperiphery of the stent body to accommodate longitudinal flexing of thestent within the segments and without interference between adjacentsegments.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 a shows a band-like element used in the inventive stents.

FIG. 1 b shows a schematic of a peak region which contains a double peakand a trough region containing a double trough.

FIG. 2 shows a flat view of a stent configuration according to theinvention.

FIG. 3 shows the pattern of FIG. 2 in a tubular stent.

FIG. 4 a shows a flat view of a stent configuration according to theinvention.

FIG. 4 b shows a flat view of a stent configuration according to theinvention.

FIG. 5 a shows a flat view of a stent configuration according to theinvention.

FIG. 5 b shows a flat view of a stent configuration according to theinvention.

FIG. 6 shows a flat view of a stent configuration according to theinvention.

FIG. 7 shows a flat view of a stent configuration according to theinvention.

FIG. 8 shows a flat view of a stent configuration according to theinvention.

FIG. 9 shows a flat view of a stent configuration according to theinvention.

FIG. 10 shows a flat view of a stent configuration according to theinvention.

FIG. 11 shows a flat view of a stent configuration according to theinvention.

FIG. 12 shows a flat view of a stent configuration according to theinvention.

FIG. 13 shows the pattern of FIG. 12 in a tubular stent.

FIG. 14 shows an expanded stent of the configuration shown in FIG. 12.

FIG. 15 shows a flat view of an alternate stent configuration accordingto the invention.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiments illustrated.

For the sake of consistency, the terms ‘peak’ and ‘trough’ shall bedefined with respect to the proximal and distal ends of the stent. Eachof the stents has a proximal end 91 and a distal end 93 and alongitudinal axis 95, as seen in FIG. 1 a. Peaks 36 are generallyconcave relative to the proximal end of the stent and generally convexrelative to the distal end of the stent. Troughs 40, on the other hand,are generally convex relative to the proximal end of the stent andgenerally concave relative to the distal end of the stent.Notwithstanding this definition, the term peak is also intended toextend to regions 48 that are generally peak-like which may,nevertheless, contain trough-like regions within the peak-like region asseen in FIG. 1 b. Similarly the term trough is also intended to extendto regions 52 that are generally trough-like which may, nevertheless,contain peak-like regions within the trough-like region as seen in FIG.1 b.

Corresponding to each peak 36 is an inner diameter peak 38 where theinner diameter of the band-like element reaches its peak. The set ofpoints on a given band-like element which are distal to inner diameterpeak 38 is denoted peak region 48. Similarly, corresponding to eachtrough 40 is an inner diameter trough 42 where the inner diameter of theband-like element reaches its trough. The set of points on a givenband-like element which are proximal to inner diameter trough 42 isdenoted trough region 52. For the sake of clarity, unless otherwiseindicated, analogous portions of stents will be similarly labeled, usingthree digit reference numerals to distinguish among the variousembodiments shown.

Also included within this definition of peak regions and trough regionsare peak regions which are comprised of multiple peaks as well as troughregions which are comprised of multiple troughs such as those shownschematically in FIG. 1 b. Peak 36 is seen to consist of two sub-peaks36 a,b and trough 40 is similarly seen to consist of two sub-troughs 40a,b. In the case of peaks containing sub-peak and troughs containingsub-troughs, the peak region 48 includes all of the points along theband-like element between the sub-peaks that make up the peak andsimilarly, the trough region 52 includes all of the points along theband-like element between the sub-troughs that make up the trough.

The inventive stents may incorporate one or more bands of a chosenwavelength. In some embodiments, the inventive stents include one ormore small amplitude, short wavelength bands to provide for flexibilityand one or more large amplitude, long wavelength bands to give sidebranch access or to provide for sections of alternative strengths suchas soft and/or stiff sections.

Turning to the Figures, FIG. 2 shows a flat view of a stentconfiguration and FIG. 3 shows the stent of FIG. 2 in tubular form. Thatis, the stent is shown for clarity in FIG. 2 in the flat and may be madefrom a flat pattern 110 (FIG. 2) which is formed into a tubular shape byrolling the pattern so as to bring edges 112 and 114 together (FIG. 2).The edges may then joined as by welding or the like to provide acylindrical configuration such as that shown generally at 115 in FIG. 3.

A more preferred method of manufacture begins with a thin walled tubewhich is then laser cut to provide the desired configuration. It mayalso be chemically etched or EDM'd (electrical discharge machined) toform an appropriate configuration.

The configuration can be seen in these Figures to be made up of one ormore spaced first band-like elements 120. First band-like elements havea generally serpentine configuration to provide continuous waves to thefirst band-like elements. The waves are characterized by a plurality ofpeaks 124 and troughs 128 taking a generally longitudinal directionalong the cylinder such that the waves in first band-like elements 120open as the stent is expanded from an unexpanded state having a firstdiameter to an expanded state having a second diameter.

The stent further comprises a plurality of spaced second band-likeelements 132 having a generally serpentine configuration to providecontinuous waves to the second band-like elements. The waves arecharacterized by a plurality of peaks 136 and troughs 140 taking agenerally longitudinal direction along the cylinder such that the wavesin the second band-like elements open as the stent is expanded from anunexpanded state having a first diameter to an expanded state having asecond diameter. First and second band-like elements are characterizedby respective wavelengths and amplitudes with the wavelength andamplitude of the second band-like elements exceeding the wavelength andamplitude of the first band-like elements.

Adjacent first band-like elements 120 and second band-like elements 132are interconnected via a plurality of interconnecting elements 144. Theends of interconnecting element are circumferentially offset from eachother.

In an embodiment, as shown in FIGS. 2 and 3, first band-like elements120 and second band-like elements 132 alternate over the length of thestent. Optionally, as shown in FIGS. 2 and 3, each end 152 of the stentmay terminate in a first band-like element. The invention also, however,contemplates each end terminating in a second band-like element, orfurther, one end terminating in a first band-like element and the otherend terminating in a second band-like element.

While a minimum of one connecting element is required to join adjacentband-like elements, two or more interconnecting elements are preferred.In one embodiment, as shown in FIGS. 2 and 3, adjacent first and secondband-like elements 120 and 132 are connected with three interconnectingelements 144. Further, in one embodiment, adjacent interconnectingelements 144 extending from peaks 136 on a first band-like element 120are spaced five peaks apart on the first band-like element whileadjacent interconnecting elements 144 extending from troughs 140 on asecond band-like element 132 are spaced three troughs apart on thesecond band-like element.

It is a further feature of the present invention that peaks 124 on firstband-like elements 120 are circumferentially displaced on the peripheryof the stent from troughs 140 on adjacent second band-like elements 132.It is desirable that peaks and troughs be displaced in the expandedstate of the stent to minimize the possibility of pinching or overlapbetween adjacent band-like elements.

Although the stent of FIG. 2 is comprised of two different wavelengthband-like elements, the invention contemplates stents with a pluralityof different wavelength band-like elements. As such, other stents mayhave three, four or more different wavelength band-like elements.

In another embodiment, the inventive stent is comprised of band-likeelements of a single wavelength, interconnected by interconnectingelements. Turning to FIGS. 4 a and 4 b, band-like elements 220 a,b areinterconnected by interconnecting elements 244 a,b. Adjacent band-likeelements 220 a,b are 180° out of phase with one another. In thecompressed state, the band-like elements consist of a plurality of peaks236 a,b and troughs 240 a,b. Peak region 248 a,b and trough region 252a,b have been shaded in one instance for illustrative purposes.

In the embodiment shown in FIG. 4 a, each interconnecting element 244 aextends between a peak region 248 a and a trough region 252 a.Rectilinear interconnecting elements 244 a consist of a first shank 280a, a second shank 284 a and a link 288 a disposed in-between the firstand second shanks 280 a and 284 a. First shank 280 a extends in alongitudinal direction from peak region 248 a and is substantiallyperpendicular to link 288 a. Second shank 284 a extends in alongitudinal direction from trough region 252 a and is perpendicular tolink 288 a.

In the embodiment shown in FIG. 4 b, the stent differs from theembodiment of FIG. 4 a in that interconnecting element 244 b extendingbetween a peak region 248 b and a trough region 252 b is curvilinearrather than rectilinear.

In both FIGS. 4 a and 4 b, the interconnecting elements are seen toemanate from the middle of the peak and trough regions.

In another embodiment, as shown in FIG. 5 a, the inventive stent iscomprised of band-like elements 320 a of a single wavelength,interconnected by interconnecting elements 344 a. Adjacent band-likeelements 320 a are 180° out of phase with one another. The band-likeelements consist of a plurality of peaks 336 a and troughs 340 a.Interconnecting elements 344 a extend between a peak region 348 a and atrough region 352 a. The peak regions 348 a and trough regions 352 afrom which interconnecting elements 344 a emanate on a given band-likeelement 320 a are seen to extend longitudinally beyond adjacent peakregions 348 a′ and trough regions 352 a′ from which no interconnectingelements extend. The extension is such that at least a portion of peakregions 348 a overlap longitudinally along the stent with at least aportion of trough region 352 a on an adjacent band-like element 320 a′.Of course, the overlap is limited to the longitudinal direction and notto the circumferential direction.

In another embodiment, as shown in FIG. 5 b, interconnecting elements344 b extend between peak region 348 b and a second closest troughregion 352 b on an adjacent band-like element. Interconnecting elements344 b are seen to be perpendicular to the longitudinal axis. As in thestent of FIG. 5 a, peak regions 348 b from which interconnectingelements 344 b extend and trough regions 352 b from whichinterconnecting elements 344 b extend may extend beyond adjacent peakregions 348 b′ and trough regions 352 b′ from which no interconnectingelements 344 b emanates.

In another embodiment, as shown in FIG. 6, adjacent band-like elements420 are in phase with each other. As in previous Figs, band-likeelements 420 are of a single wavelength, interconnected byinterconnecting elements 444. The band-like elements consist of aplurality of peaks 436 and troughs 440. Interconnecting elements 444extend at an oblique angle relative to the longitudinal axis of thestent between a peak region 448 and a trough region 452. As such, endsof interconnecting elements 444 are circumferentially offset relative toeach other. The exact angle will, of course, depend on the region fromwhich the interconnecting elements extend, as well as on whetherinterconnecting elements interconnect nearest peaks and troughs, nextnearest peaks and troughs or peaks and troughs that are furtherseparated.

In FIGS. 5 a, 5 b and 6, the interconnecting elements are seen toemanate from the sides of the peak and trough regions.

Although for the embodiments of FIGS. 1-6, the interconnecting elementsextend from peak regions on band-like elements to trough regions onadjacent band-like elements, the invention further contemplatesinterconnecting elements extending from a position between a peak regionand an adjacent trough region on a band-like element to a positionintermediate a trough region and a peak region on an adjacent secondband-like element as in FIG. 7.

In the embodiment of FIG. 7, interconnecting elements are seen to extendfrom a region between the peak region and the trough region on aband-like element. The stent is formed of adjacent band-like elements520 which are 180° degrees out of phase with one another.Interconnecting elements 544 extend from a region intermediate a peakregion 548 and a trough region 552 on a band-like element to a regionintermediate a peak region 548 and a trough region 552 on an adjacentband-like element. Interconnecting elements 544 consist of a first shank560, a second shank 564, and an intermediate member 568 disposedin-between first and second shanks 560 and 564. First shank 560 andsecond shank 564 are substantially perpendicular to intermediate member568 which extends in the longitudinal direction. Although not depicted,the region from which interconnecting elements 544 emanate may be midwaybetween peaks and troughs.

The embodiment of FIG. 7 also differs from the embodiments of FIGS. 2-6in the orientation of the interconnecting elements. Whereas theinterconnecting elements in FIGS. 2-6 are all similarly oriented, in theembodiment of FIG. 7, the orientation of interconnecting elementsalternates between adjacent pairs of adjacent band-like elements.Specifically, second shanks 564′ of interconnecting elements 544′ areseen to be displaced in a clockwise circumferential direction along thestent relative to first shanks 560′, and seconds shank 564″ ofinterconnecting elements 544″ are seen to be displaced in acounterclockwise circumferential direction along the stent relative towhile first shank 560″.

This feature is also seen in the embodiment of FIG. 8 in which adjacentin-phase band-like elements 620 are interconnected by interconnectingelements 644. Interconnecting elements 644 extend at an oblique anglerelative to the longitudinal axis of the stent between a peak region 648and a trough region 652. As in FIG. 7, the orientation ofinterconnecting elements alternates between adjacent pairs of adjacentband-like elements. Specifically, the distal ends of interconnectingelements 644′ are seen to be oriented in a counterclockwisecircumferential direction along the stent relative to the proximal endof the interconnecting elements while the distal ends of interconnectingelements 644″ are seen to be displaced in a clockwise circumferentialdirection along the stent relative to the proximal ends.

Although in the embodiments of FIGS. 2-8, adjacent bands are connectedby five interconnecting elements, additional or fewer interconnectingelements may be used. Further, while interconnecting elements are shownspaced three peaks apart and three troughs apart, other separations arecontemplated as well.

In the embodiment of FIG. 9, each band-like element 720 is seen tocomprise peaks 736 of more than one amplitude and troughs 740 of morethan one amplitude. Large amplitude peaks 736 a and small amplitudepeaks 736 b alternate as do large amplitude troughs 740 a and smallamplitude troughs 740 b. As in the previous embodiments, theinterconnecting elements are oriented at an oblique angle relative tothe longitudinal axis 795 of the stent. More generally, the invention isdirected at stents comprising band-like elements whose amplitude variesalong the band-like element.

In another embodiment of the invention, as shown in FIG. 10, eachband-like element 820 is seen to comprise peaks 836 of more than oneamplitude and troughs 840 of more than one amplitude, however, peaks ofthe same amplitude are grouped together within a band-like element asare troughs of the same amplitude. It is further noted that in theembodiment of FIG. 10, the location of a group of peaks of givenamplitude in a band-like element varies circumferentially along thelength of the stent. Interconnecting elements 844 connect peaks 836 andtroughs 840 in adjacent band-like elements 820. Where several peaks ofdifferent amplitudes are present in a band-like element, the inventionfurther contemplates the possibility of interconnecting elementsextending from the large peaks 836 a to large troughs 840 a as in FIG. 9as well as the possibility of interconnecting elements extending fromlarge peaks to small troughs or from small peaks 836 b to large troughs840 a as in FIG. 10. Further, the interconnecting elements between anytwo adjacent band-like elements may be of different lengths from oneanother as seen in FIG. 10 and commence at different longitudinalpositions within a band-like element and terminate at differentlongitudinal positions within a band-like element. Interconnectingelement 844 a is seen to be longer than interconnecting element 844 b.As in the previous embodiments, the interconnecting elements areoriented at an oblique angle relative to the longitudinal axis 895 ofthe stent. In the embodiment of FIG. 10, interconnecting element 844 ais seen to be oriented at a smaller oblique angle relative to thelongitudinal axis of the stent than interconnecting element 844 b. As isapparent from FIG. 10, the invention is also directed to stentscomprised of band-like elements whose wavelength varies along a givenband-like element. Region 898 and region 899 of band-like element arecharacterized by different wavelengths.

It is also noted that in the embodiment of FIG. 10, all of the troughs840 a,b in a given band-like element 820 are aligned longitudinallyalong the stent and differ only in their circumferential position alongthe stent.

It is further noted in the embodiment of FIG. 10, the stent comprises afirst group of interconnecting elements 844 a and a second group ofinterconnecting elements 844 b. The interconnecting elements of thefirst group are all parallel to one another and disposed at a differentoblique angle relative to the longitudinal axis than the members of thesecond group which are all parallel to one another. As such, theinvention contemplates stents having several different groups ofobliquely disposed interconnecting elements where the oblique anglediffers from group to group.

In another embodiment of the invention, as shown in FIG. 11, eachband-like element 920 is seen to comprise peaks 936 a,b of differentamplitudes and troughs 940 of different amplitudes, however, peaks ofthe same amplitude are grouped together within a band-like element asare troughs of the same amplitude. It is further noted that in theembodiment of FIG. 11 the location of groups of peaks of given amplitudein a band-like element varies circumferentially along the length of thestent. Interconnecting elements 944 connect large amplitude peaks 936 aand small amplitude troughs 940 b in adjacent band-like elements 920.Similarly, interconnecting elements 944 also connect small amplitudepeaks 936 b and large amplitude troughs 940 a.

The invention also contemplates stents similar to that shown in FIG. 11in which interconnecting elements extend from large peaks 936 a to largetroughs 940 a, as in FIG. 9. Similarly, interconnecting elements mayextend from small peaks 936 b to small troughs 940 b.

Further, the interconnecting elements between any two adjacent band-likeelements may be of different lengths from one another and disposed atdifferent oblique angles.

As is apparent from FIG. 11, the invention is also directed to stentscomprised of band-like elements whose wavelength varies along a givenband-like element. Region 998 and region 999 of band-like element 920are characterized by different wavelengths.

It is also noted that in the embodiment of FIG. 11 the large amplitudeportions 999 of band-like element 920 are symmetrically disposed aboutthe center 1001 of the band-like element as are the small amplitudeportions 998. The center 1001 of the band-like element is defined as aring that runs along a path that is midway between the large peaks 936 aand large troughs 940 a of the band-like element. This feature may alsobe seen in the embodiment of FIG. 9.

The invention is also directed to a tubular, flexible, expandable stenthaving a longitudinal axis, comprising one or more cylindrical shapedfirst segments. Cylindrical shaped first segments 20 as seen in FIG. 1,have first struts 23 having first 25 and second 27 ends. First segments20 are defined by a member formed in an undulating pattern ofinterconnected paired first struts 23, in which adjacent pairs of firststruts 29′ and 29″ in a given first segment 20 are interconnected atopposite ends 31′ and 31″, respectively. Adjacent segments areinterconnected.

The stent may be seen more clearly in FIGS. 2-8. As shown, the stent ofFIG. 3, in addition to comprising first segments 120 which are definedby an undulating pattern of interconnected paired first struts 123 inwhich adjacent pairs of first struts 129′ and 129″ in a given firstsegment 120 are interconnected at opposite ends 131′ and 131″,respectively, the stent further comprises one or more cylindrical shapedsecond segments 132, each second segment being defined by a memberformed in an undulating pattern of interconnected paired second struts135 and in which adjacent pairs of second struts 137′ and 137″ in agiven second segment 132 are interconnected at opposite ends 139′ and139″, respectively. First struts 123 are shorter than second struts 135.First segments 120 are formed of a number of first struts 123 and secondsegments 132 formed of a number of second struts 135, the number offirst struts in a first segment exceeding the number of second struts ina second segment. First and second segments 120 and 132 are aligned on acommon longitudinal axis 195 to define a generally tubular stent body,shown generally at 115. First and second segments 120 and 132 alternatealong the stent body. Adjacent first and second segments 120 and 132 areconnected by a plurality of interconnecting elements 144. Eachinterconnecting element 144 extends from an end 131″ of paired firststruts on a first segment 120 to an end 139″ of paired second struts onan adjacent second segment 132. The ends of interconnecting elements 144are circumferentially offset relative to each other.

Desirably, upon expansion of stent 115, paired struts 129″ and 137″ ofadjacent segments 120 and 132 are displaced relative to each other aboutthe periphery of the stent body to accommodate longitudinal flexing ofthe stent within the segments and without interference between adjacentsegments.

In the embodiments as shown in FIGS. 4 a, b, cylindrical shaped segments220 a,b are formed of interconnected struts 223 a,b having first 225 andsecond 227 ends. Adjacent pairs of struts 229 a,b′ and 229 a,b″ in agiven segment 220 a,b are interconnected at opposite ends 231 a,b′ and231 a,b″, respectively. Adjacent segments are connected by a pluralityof interconnecting elements 244 a,b. Each interconnecting element 244a,b extends from an end of paired struts 231 a,b″ on a segment to an endof paired struts 231 a,b′ on an adjacent segment. First end 245 a,b andsecond end 247 a,b of interconnecting elements 244 a,b are seen to becircumferentially displaced along the stent.

Similar structure, denoted by similar reference numerals may be found inthe stents of FIGS. 5 a,b, and 6-8.

In particular, in the embodiment as shown in FIG. 8, cylindrical shapedsegments 620 are formed of interconnected struts 623, having first 625and second 627 ends. Segments 620 are defined by a member formed in anundulating pattern of interconnected paired struts 623 in which adjacentpairs of struts 629′ and 629″ in a given segment 620 are interconnectedat opposite ends 631′ and 631″, respectively. Segments 620 are alignedon a common longitudinal axis 695 to define a generally tubular stentbody. Adjacent segments are connected by a plurality of interconnectingelements 644 (and 644′) having first 645 (645′) and second 647 (647′)ends, each interconnecting element 644 (644′) extending from an end ofpaired struts 631″ on a segment to an end of paired struts 631′ on anadjacent segment. First end 645 (645′) and second end 647 (647″) areseen to be circumferentially displaced along the stent.

Additional embodiment of the stents are shown in FIGS. 12-15. FIG. 12and FIG. 13 show a fragmentary flat view of an unexpanded stentconfiguration and the actual tubular stent (unexpanded), respectively.That is, the stent is shown for clarity in FIG. 12 in the flat and maybe made from a flat pattern 1110 (FIG. 12) which is formed into atubular shape by rolling the pattern so as to bring edges 1112 and 1114together (FIG. 12). The edges may then joined as by welding or the liketo provide a configuration such as that shown in FIG. 13.

The configuration can be seen in these Figures to be made up of aplurality of adjacent segments generally indicated at 1116, each ofwhich is formed in an undulating flexible pattern of substantiallyparallel struts 1118. Pairs of struts are interconnected at alternatingend portions 1119 a and 1119 b. As is seen in FIG. 12, theinterconnecting end portions 1119 b of one segment are positionedopposite interconnecting end portions 1119 a of adjacent segments. Theend portions as shown are generally elliptical but may be rounded orsquare or pointed or the like. Any configuration of end portions isacceptable so long as it provides an undulating pattern, as shown. Whenthe flat form 1110 is formed into an unexpanded tube as shown in FIG.13, the segments are cylindrical but the end portions 1119 of adjacentsegments remain in an opposed position relative to each other.

A more preferred method of manufacture begins with a thin walled tubewhich is then laser cut to provide the desired configuration. It mayalso be chemically etched or EDM'd (electrical discharge machined) toform an appropriate configuration.

Interconnecting elements 1120 extend from one end portion 1119 of onesegment 1116 to another end portion 1119 of another adjacent segment1116 but not to an oppositely positioned end portion 1119 of an adjacentsegment 1116. There are at least three struts included between thepoints on each side of a segment 1116 at which an interconnectingelement 1120 contacts an end portion 1119. This results in theinterconnecting elements 1120 extending in an angular direction betweensegments around the periphery of the tubular stent. Interconnectingelements 1120 are preferably of the same length but may vary from onesegment to the other. Also, the diagonal direction may reverse from onesegment to another extending upwardly in one case and downwardly inanother, although all connecting elements between any pair of segmentsare substantially parallel. FIG. 12, for example shows them extendingdownwardly, right to left. Upwardly would extend up left to right inthis configuration.

As a result of this angular extension of the interconnecting elements1120 between adjacent segments and loops, upon expansion of the stent asseen in FIG. 14, the closest adjacent end portions 1119 between segments1116 are displaced from each other and are no longer opposite each otherso as to minimize the possibility of binding or overlapping betweensegments, i.e., pinching.

The number of interconnecting elements 1120 may vary depending oncircumstances in any particular instance. Three per segment aresatisfactory for the configuration shown and at least three will be usedtypically.

The alternate design shown in FIG. 15 includes longer struts 1118 a inthe two end segments 1116 a than in the intermediate segments 1116. Thisallows the end segments (1116 a) to have less compression resistancethan the intermediate segments (1116), providing a more gradualtransition from the native vessel to the support structure of the stent.Otherwise, the configuration is the same as that shown in FIG. 12.

As indicated in the Figures, the invention contemplates a variation ofinterconnecting element shapes ranging from rectilinear to curvilinear.The invention further contemplates embodiments in which allinterconnecting elements are similarly oriented as well as embodimentsin which adjacent sets of interconnecting elements extending betweenadjacent pairs of segments are oppositely oriented (e.g., FIGS. 7 and8). The invention also contemplates the use of interconnecting elementswhich extend from a range of positions along the segments, ranging fromvarious positions in the area in which paired struts are interconnectedto other positions along the struts.

The invention also contemplates the possibility of interconnectingelements extending at an oblique angle relative to the longitudinal axisof the stent and connecting adjacent peaks and troughs on adjacentsegments as well as peaks and troughs on adjacent segments which areseparated by one or more peaks and/or troughs.

The invention also contemplates reversing the orientation ofinterconnecting elements as shown in FIGS. 7 and 8.

Finally, there are preferably at least three interconnecting elementsjoining adjacent first and second segments although fewer or additionalinterconnecting elements are also contemplated.

It is understood that the peaks and troughs of the present inventionneed not be rounded, as shown in the Figures. The peaks and troughs maybe bulbous, triangular, square, pointed, or otherwise formed ofinterconnected straight sections.

As already indicated, this invention is applicable to self-expandingconfigurations, mechanically expandable configurations and to a widevariety of materials, including both metal and plastic and any othermaterial capable of functioning as an expandable stent. For example, thestent may be of metal wire or ribbon such as tantalum, stainless steelor the like. It may be thin-walled. It may be of shape memory alloy suchas Nitinol or the like, etc. The interconnecting elements may be formedintegrally with the band-like elements (or segments) or may be bondedthereto via such methods as adhesive bonding, welding or any other knownmethod of bonding.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and this description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

1-37. (Canceled)
 38. A stent comprising a first loop containing section,the first loop containing section arranged generally in thecircumferential direction, the loops in said first loop containingsection occurring at a first frequency; a second loop containingsection, the second loop containing section arranged generally in thecircumferential direction, the loops in said second loop containingsection also occurring at said first frequency; and a third loopcontaining section, the loops in said third loop containing sectionoccurring at a second frequency that is higher than said firstfrequency, the third loop containing section disposed in the generallycircumferential space between said first and second loop containingsections and alternately joined to said first and second loop containingsections such that said first and second loop containing sections arejoined together through the third loop containing section withoutconnection directly between the first and second loop containingsections, wherein the first and second loop containing sections havethree cycles for every five cycles of said third loop containingsection, wherein the first loop containing section or the second loopcontaining section and the third loop containing section form at leastone cell, the first loop containing section or the second loopcontaining section in the at least one cell further has at least oneloop longitudinally shorter than another loop in the first loopcontaining section or the second loop containing section.
 39. A stentcomprising a first loop containing section, the first loop containingsection arranged generally in the circumferential direction, the loopsin said first loop containing section occurring at a first frequency; asecond loop containing section, the second loop containing sectionarranged generally in the circumferential direction, the loops in saidsecond loop containing section also occurring at said first frequencyand a third loop containing section, the loops in said third loopcontaining section occurring at a second frequency that is higher thansaid first frequency, the third loop containing section disposed in thegenerally circumferential space between said first and second loopcontaining sections and alternately joined to said first and second loopcontaining sections such that said first and second loop containingsections are joined together through the third loop containing sectionwithout connection directly between the first and second loop containingsections, wherein the first and second loop containing sections havefewer cycles than the third loop containing section, wherein the firstloop containing section or the second loop containing section and thethird loop containing section form at least one cell, the first loopcontaining section or the second loop containing section in the at leastone cell further has at least one loop longitudinally shorter thananother loop in the first loop containing section or the second loopcontaining section.